JP2016091711A - Secondary battery and method of manufacturing secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the characteristics of a secondary battery.SOLUTION: A lithium ion secondary battery includes: a cylindrical battery can 10 housing an electrode group and having a bottom, a side part and an opening; and a battery lid 30 to seal the opening of the batty can 10. The battery can 10 is made of an aluminum-containing material, a projecting portion (positive electrode external terminal) 10a is provided at the bottom of the battery can 10, an outside projecting portion (negative electrode external terminal) 51a is provided on a side of the battery lid 30, and the thickness of the projecting portion (positive electrode external terminal) 10a is thicker than the thickness of the side part of the battery can 10. By forming the projecting portion (positive electrode external terminal) 10a to be thick in the manner, connection resistance at a positive electrode external terminal of a secondary battery can be reduced. The battery can 10 can be formed by an impact molding method.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a secondary battery.

  A lithium ion secondary battery is a high energy density secondary battery, and is used as a power source for portable devices such as notebook computers and mobile phones by taking advantage of its characteristics. There are various types of lithium ion secondary batteries. Cylindrical lithium ion secondary batteries employ a wound structure of a positive electrode plate, a negative electrode plate, and a separator. For example, a positive electrode material and a negative electrode material are respectively applied to two strip-shaped metal foils, a separator is sandwiched therebetween, and these laminated bodies are wound in a spiral shape to form a wound group. The wound group is accommodated in a cylindrical battery can serving as a battery container, and after injecting an electrolytic solution, the cylindrical lithium ion secondary battery is formed.

  In recent years, lithium ion secondary batteries are expected to be used not only for consumer applications such as portable devices but also for large-scale power storage systems for natural energy such as solar power and wind power generation. In a large-scale power storage system, the amount of power per system is required on the order of several MWh.

  In such a large-capacity secondary battery, various improvements are desired in its configuration and manufacturing method.

  For example, Patent Document 1 below discloses a method of forming a battery can by molding an aluminum plate with a mold.

JP 2006-338992 A

  When using the above-described large-capacity secondary battery, the capacity per battery is large, and a plurality of batteries may be used as a system. Improvement is necessary.

  In particular, when the constituent material of the battery can is thinned and a plurality of batteries are connected as a system, the external connection resistance becomes high.

  In particular, when the external terminal is thinned or miniaturized, the area through which the current flows becomes small, and the resistance becomes high.

  The secondary battery shown in the typical embodiment disclosed in the present application is as follows.

  A cylindrical battery container that houses an electrode group, and includes a battery container having a bottom part, a side part, and an opening part, and a battery lid that seals the opening part of the battery container. The battery container is made of a material containing aluminum, the positive electrode external terminal is provided at the bottom of the battery container, the negative electrode external terminal is provided on the battery lid side, and the thickness of the positive electrode external terminal in the height direction is increased. Is thicker than the thickness of the side of the battery container.

  The manufacturing method of the secondary battery shown in the representative embodiment disclosed in the present application is as follows.

  (A) a step of forming an electrode group by winding a positive electrode plate and a negative electrode plate through a separator, (b) a cylindrical battery container having a bottom part, a side part, and an opening part And (c) sealing the opening of the battery container with a battery lid so that the positive electrode side of the electrode group contacts the bottom. The battery container is made of a material containing aluminum, and the positive electrode external terminal is provided at the bottom of the battery container, and the thickness of the positive electrode external terminal is thicker than the thickness of the side part of the battery container.

  The battery container is formed by an impact molding method. For example, the battery container is formed by fluidly deforming an aluminum-containing material by an impact when the rod-shaped member is driven into the aluminum-containing material, and raising the aluminum-containing material along the side surface of the rod-shaped member. Is done.

  Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  According to the present invention, the characteristics of the secondary battery can be improved. In particular, the connection resistance at the positive electrode external terminal of the secondary battery can be reduced.

3 is a schematic diagram illustrating a configuration of a battery can for a lithium ion secondary battery according to Embodiment 1. FIG. 1 is a schematic diagram illustrating a configuration of a lithium ion secondary battery according to Embodiment 1. FIG. It is sectional drawing which shows the manufacturing process of the battery can by an impact molding method. It is sectional drawing which shows the manufacturing process of the battery can by an impact molding method. It is sectional drawing which shows the other example of the manufacturing process of a battery can. It is a figure which shows the structure of the lithium ion secondary battery of Embodiment 2, (A) is sectional drawing, (B) is the top view seen from the upper side, (C) is the top view seen from the lower side It is. (A) And (B) is a perspective view which shows the manufacturing process of the lithium ion secondary battery of Embodiment 2. FIG. 7 is a cross-sectional view showing a manufacturing process of the lithium ion secondary battery of Embodiment 2. FIG. 7 is a cross-sectional view showing a manufacturing process of the lithium ion secondary battery of Embodiment 2. FIG. 7 is a cross-sectional view showing a manufacturing process of the lithium ion secondary battery of Embodiment 2. FIG. 7 is a cross-sectional view showing a manufacturing process of the lithium ion secondary battery of Embodiment 2. FIG. 7 is a cross-sectional view showing a manufacturing process of the lithium ion secondary battery of Embodiment 2. FIG. It is sectional drawing which shows the manufacturing process of the battery can by an impact molding method. 4 is a cross-sectional view showing a configuration of a lithium ion secondary battery according to Embodiment 3. FIG.

(Embodiment 1)
FIG. 1 is a schematic diagram showing a configuration of a battery can for a lithium ion secondary battery according to the present embodiment. FIG. 2 is a schematic diagram showing the configuration of the lithium ion secondary battery of the present embodiment.

  A battery can (also referred to as a battery container) 10 shown in FIG. 1 is a cylindrical container, and has a bottom surface (also referred to as a bottom portion), a side surface (also referred to as a side portion), and an upper opening. The battery can 10 has a convex portion (also referred to as a thick film portion, an outer protrusion, or a positive electrode external terminal) 10a that serves as a positive electrode external terminal on the bottom surface thereof. The thickness Ta of the battery can at the convex portion 10a is larger than the thickness Tb of the battery can at the side surface (Ta> Tb). The battery can 10 shown in FIG. 1 is made of an aluminum material.

  In such a battery can 10, the electrode group 20 is inserted (contained), and the battery lid 30 is welded to the opening of the battery can 10, thereby sealing the opening of the battery container and forming a battery. (FIG. 2). At this time, the plus side of the electrode group 20 is inserted as the lower side (bottom side), and the electrode group 20 and the convex portion 10a are electrically connected. Further, the negative side of the electrode group 20 is the upper side (battery cover 30 side), and, for example, a negative electrode pole column serving as a negative electrode external terminal protrudes from an opening (also referred to as a hole) of the battery cover 30. The battery manufacturing process will be described in detail in Embodiment 2.

  The battery can 10 shown in FIG. 1 is formed by an impact molding method. 3 and 4 are cross-sectional views showing the manufacturing process of the battery can by the impact molding method. First, as shown in FIG. 3, an aluminum material (aluminum lump) 101 is set in a cavity (also referred to as a female portion or a die) 100 (left diagram in FIG. 3). Next, a punch rod (also referred to as a male portion, a punch portion, or a rod-like member) 103 having a diameter corresponding to the inner diameter of the battery can is driven into the aluminum material 101 (center view in FIG. 3). The aluminum material 101 flows and deforms due to the impact of the punch rod 103 being driven, and rises along the side surface of the punch rod 103 from the gap between the punch rod 103 and the cavity 100 (right diagram in FIG. 3). At this time, by providing the recess 100a at the center of the cavity, the impact of the punch rod 103 is difficult to be transmitted in the vicinity of the recess 100a. For this reason, the aluminum film at the center of the cavity 100 is thicker than the aluminum film formed along the side surface of the punch rod 103. Thereafter, as shown in FIG. 4, the battery can 10 is formed by peeling the aluminum material 101 from the punch rod 103 and the cavity 100.

  Thus, according to the impact molding method, the battery can 10 can be formed quickly in a short process. Moreover, the weight reduction of the battery can 10 can be achieved by using aluminum as a material. In particular, aluminum has high spreadability, and the battery can 10 can be made thin. Also in this respect, the battery can 10 can be reduced in weight.

  Further, according to the impact molding method, it is possible to integrally mold the convex portion 10a serving as the positive electrode external terminal. For this reason, electrical resistance can be reduced compared with the case where a positive electrode external terminal is formed with another material and electrically connected. Further, when the side surface of the battery can 10 is thinned and the bottom surface is similarly thinned, the external connection resistance is increased. On the other hand, in the convex portion 10a serving as the positive electrode external terminal, the external connection resistance can be reduced by increasing the thickness of the aluminum film.

  Further, by connecting the battery can 10 side to the positive electrode, that is, the positive side of the electrode group 20, the electrode group 20 using the aluminum material as the positive electrode plate and the material of the battery can 10 become the same material, and their electrical stability. And electrical connectivity is improved. For example, the corrosion of the battery can can be suppressed as compared with the case where the positive electrode plate and the battery can are made of different materials. In particular, in a large-capacity lithium ion secondary battery, the charge / discharge reaction at the positive electrode is actively performed, so that the effect of improving the electrical stability at the positive electrode is great.

  In the impact molding method, the shape and thickness of the protrusion 10a can be adjusted by adjusting the impact of the punch rod 103 and the degree of flow deformation of the aluminum material 101. However, when this adjustment is difficult, as shown in FIG. 5, after forming the convex portion 10a, the convex portion 10a may be cut to further adjust the shape and thickness of the convex portion 10a. . FIG. 5 is a cross-sectional view showing another example of the battery can manufacturing process.

  Next, the internal configuration of the battery can will be described. The electrode group 20 sealed inside the battery can 10 includes a positive electrode plate, a negative electrode plate, and a separator. The electrode group 20 is formed by winding around a shaft core with a separator between the positive electrode plate and the negative electrode plate. In addition, an electrolytic solution is sealed inside the battery can 10.

  When charging the lithium ion secondary battery, a charger is connected between the positive electrode and the negative electrode. At the time of charging, lithium ions inserted into the positive electrode active material are desorbed and released into the electrolytic solution. The lithium ions released into the electrolytic solution move in the electrolytic solution, pass through a separator made of a microporous film, and reach the negative electrode. The lithium ions that have reached the negative electrode are inserted into the negative electrode active material constituting the negative electrode.

  When discharging, an external load is connected between the positive electrode and the negative electrode. At the time of discharging, the lithium ions inserted into the negative electrode active material are desorbed and released into the electrolytic solution. At this time, electrons are emitted from the negative electrode. Then, the lithium ions released into the electrolytic solution move in the electrolytic solution, pass through a separator made of a microporous film, and reach the positive electrode. The lithium ions reaching the positive electrode are inserted into the positive electrode active material constituting the positive electrode. At this time, when lithium ions are inserted into the positive electrode active material, electrons flow into the positive electrode. In this way, discharge is performed by the movement of electrons from the negative electrode to the positive electrode.

  In this manner, charging / discharging can be performed by inserting and desorbing lithium ions between the positive electrode active material and the negative electrode active material.

  Next, a positive electrode plate, a negative electrode plate, a separator, and an electrolytic solution that are components of the lithium ion secondary battery of the present embodiment will be described below.

1. Positive electrode The positive electrode plate is composed of a current collector and a positive electrode mixture formed on the current collector. The positive electrode mixture is a layer including at least a positive electrode active material provided on the current collector. The positive electrode mixture is formed (applied) on both surfaces of the current collector, for example.

  As the positive electrode active material, lithium manganate, lithium iron phosphate, or the like can be used.

2. Negative electrode The negative electrode plate is composed of a current collector and a negative electrode mixture formed on both surfaces thereof. The negative electrode mixture contains a negative electrode active material that can electrochemically occlude and release lithium ions.

  Examples of the negative electrode active material include carbonaceous materials, metal oxides such as tin oxide and silicon oxide, metal composite oxides, lithium alloys such as lithium alone and lithium aluminum alloys, metals that can form alloys with lithium such as Sn and Si, and the like Can be used. These may be used alone or in combination of two or more. Among these, a carbonaceous material or a lithium composite oxide is preferable from the viewpoint of safety.

  The metal composite oxide is not particularly limited as long as it can occlude and release lithium, but Ti (titanium), Li (lithium), or one containing both Ti and Li has a high current density charge / discharge. It is preferable from the viewpoint of characteristics.

3. Separator A separator is particularly suitable if it has ion permeability while electrically insulating between the positive electrode plate and the negative electrode plate, and has resistance to oxidation on the positive electrode side and reducibility on the negative electrode side. There is no limit. As a material (material) of the separator satisfying such characteristics, a resin, an inorganic material, glass fiber, or the like is used.

4). Electrolytic Solution The electrolytic solution of the present embodiment is composed of a lithium salt (electrolyte) and a non-aqueous solvent that dissolves the lithium salt. You may add an additive as needed.

  The lithium salt is not particularly limited as long as it is a lithium salt that can be used as an electrolyte of a non-aqueous electrolyte for a lithium ion battery. For example, the following inorganic lithium salts, fluorine-containing organic lithium salts, oxalate borate salts, etc. Is mentioned.

Examples of the inorganic lithium _{salt, LiPF 6, LiBF 4, LiAsF} 6, LiSbF inorganic fluoride salts and the like _6, LiClO _4, Libro 4, LiIO and perhalogenate such as _4, an inorganic chloride salts such as LiAlCl _4, etc. Is mentioned.

Examples of the fluorine-containing organic lithium salt include perfluoroalkane sulfonates such as LiCF ₃ SO ₃ ; LiN (CF ₃ SO ₂ ) ₂ , LiN (CF ₃ CF ₂ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C Perfluoroalkanesulfonylimide salt such as ₄ F ₉ SO ₉ ); perfluoroalkanesulfonylmethide salt such as LiC (CF ₃ SO ₂ ) ₃ ; Li [PF ₅ (CF ₂ CF ₂ CF ₃ )], Li [PF ₄ (CF ₂ CF ₂ CF ₃ ) ₂ ], Li [PF ₃ (CF ₂ CF ₂ CF ₃ ) ₃ ], Li [PF ₅ (CF ₂ CF ₂ CF ₂ CF ₃ )], Li [PF ₄ (CF _{2 CF 2 CF 2 CF 3) 2} ], Li [PF 3 (CF 2 CF 2 CF 2 CF 3) 3] fluoroalkyl hexafluorophosphate salts such like.

  Examples of the oxalatoborate salt include lithium bis (oxalato) borate and lithium difluorooxalatoborate.

These lithium salts may be used alone or in combination of two or more. Among them, lithium hexafluorophosphate (LiPF ₆ ) is preferable when comprehensively judging the solubility in a solvent, charge / discharge characteristics in the case of a secondary battery, output characteristics, cycle characteristics, and the like.

(Embodiment 2)
6A to 6C are diagrams illustrating a configuration of the lithium ion secondary battery of the present embodiment. (A) is sectional drawing, (B) is the top view seen from the upper side, (C) is the top view seen from the lower side. Also in the lithium ion secondary battery of the present embodiment, the electrode group 20 is inserted into the battery can 10 and the battery lid 30 is welded to the opening of the battery can 10 as in the case of the first embodiment. A battery is formed.

  That is, a battery can (also referred to as a battery container) 10 illustrated in FIG. 6 is a cylindrical container, and has a bottom surface (also referred to as a bottom portion), a side surface (also referred to as a side portion), and an upper opening. On the bottom surface of the battery can 10, the outer central portion has a convex portion 10 a serving as a positive electrode external terminal. A concave portion (groove) 11 is provided in the convex portion 10a. The recess 11 serves as a connection portion with a bolt (see FIG. 14), and a screw groove (not shown) is formed on the side surface thereof. The diameter of the convex portion 10a is 24 mm, and the diameter of the concave portion 11 is 5 to 10 mm.

  Further, on the bottom surface of the battery can 10, a convex portion (also referred to as an inner protrusion) 12 is provided at the inner central portion. The diameter of the convex part 12 is 15-25 mm. The convex portion 12 is fitted into the concave portion of the positive electrode current collecting ring 40 (see the concave portion 42 in FIG. 8). And also in the battery can 10 of this Embodiment, the thickness (Ta) of the battery can in the convex part 10a is larger than the thickness (Tb) of the battery can in a side surface (refer FIG. 10). Thus, the external connection resistance can be reduced by increasing the thickness of the aluminum film in the convex portion 10a serving as the positive electrode external terminal. Moreover, in this Embodiment, since the convex part 12 is provided also inside the battery can 10, external connection resistance can be reduced. The thickness of the convex portion 12 is Tc (see FIG. 10).

  The electrode group 20 is inserted into (accommodated in) such a battery can 10, and the battery lid 30 is welded to the opening of the battery can 10, thereby sealing the opening of the battery container and forming a battery ( FIG. 6). At this time, the plus side of the electrode group 20 is inserted as the lower side (bottom side), and the electrode group 20 and the convex portion 10a are electrically connected. Further, the negative side of the electrode group 20 is the upper side (battery cover 30 side), and, for example, a negative electrode pole column serving as a negative electrode external terminal protrudes from an opening (also referred to as a hole) of the battery cover 30. The electrode group 20 includes a positive electrode plate, a negative electrode plate, and a separator as in the case of the first embodiment. The electrode group 20 is formed by winding around a shaft core with a separator between the positive electrode plate and the negative electrode plate. In addition, an electrolytic solution is sealed inside the battery can 10. As the positive electrode plate, the negative electrode plate, the separator, and the electrolytic solution, the materials described in Embodiment 1 can be used as appropriate.

  7-12 is a figure which shows the manufacturing process of the lithium ion secondary battery of this Embodiment, FIG. 7 is a perspective view, FIGS. 8-12 is sectional drawing. While explaining the manufacturing method of the lithium ion secondary battery of this Embodiment, referring to FIGS. 7-12, the structure of a lithium ion secondary battery (FIG. 6) is clarified more.

1. Formation of Positive Electrode Plate As shown in FIG. 7A, the positive electrode plate 21 has a current collector 21a and a positive electrode mixture 21b formed thereon. A positive electrode lead piece 21c is provided at the end of the current collector 21a.

  The current collector 21a is a thin flat plate (also referred to as an aluminum foil) made of aluminum or an aluminum alloy. The positive electrode mixture 21b is a layer having a lithium compound that is a positive electrode active material.

  An example of a method for forming the positive electrode plate 21 will be described. For example, an aluminum foil having a rectangular shape with a short side (width) of 350 mm and a thickness of about 20 μm is prepared. Next, a positive electrode material is applied on the aluminum foil with a width of about 300 mm. This positive electrode material is applied along one long side of the aluminum foil, and a region having a width of 50 mm along the other long side is an uncoated portion. Then, a drying process is performed and it compacts with a press. Next, by cutting, a positive electrode plate having a width of 350 mm can be formed. At the time of the cutting, a notch is made in the uncoated part, and the remaining part of the notch is used as a positive electrode lead piece 21c. The width of the positive electrode lead piece 21c is, for example, about 10 mm, and the interval between the adjacent positive electrode lead pieces 21c is about 20 mm.

2. Formation of Negative Electrode Plate As shown in FIG. 7A, the negative electrode plate 22 includes a current collector 22a and a negative electrode mixture 22b formed on the current collector 22a. A negative electrode lead piece 22c is provided at the end of the current collector 22a.

  The current collector 22a is a thin flat plate (also referred to as copper foil) made of copper or a copper alloy. The negative electrode mixture 22b is a layer having a negative electrode active material.

  An example of a method for forming the negative electrode plate 22 will be described. For example, a copper foil having a rectangular shape with a short side (width) of 350 mm and a thickness of about 10 μm is prepared. Next, a negative electrode material is applied on the copper foil with a width of about 300 mm, for example. This negative electrode material is applied along one long side of the copper foil, and a region having a width of 50 mm along the other long side is an uncoated portion. Then, a drying process is performed and it compacts with a press. Next, by cutting, a negative electrode plate having a width of 350 mm can be formed. At the time of the cutting, a notch is made in the uncoated part, and the remaining part of the notch is used as the negative electrode lead piece 22c. For example, the width of the negative electrode lead piece 22c is about 10 mm, and the interval between the adjacent negative electrode lead pieces 22c is about 20 mm.

3. Formation of Electrode Group As shown in FIG. 7B, the positive electrode plate 21 and the negative electrode plate 22 are wound around the shaft core 25 with the separators 23 and 24 interposed therebetween so that they do not directly contact each other. As the separators 23 and 24, for example, polyethylene separators having a thickness of about 30 μm are used. The shaft core 25 has a cylindrical shape and is made of, for example, a polypropylene material. At the time of winding, the positive electrode plate 21 and the negative electrode plate 22 are overlapped and wound so that the respective lead pieces (21c, 22c) protrude from the opposite ends. The lengths of the positive electrode plate 21, the negative electrode plate 22, and the separators 23 and 24 are adjusted, and the electrode group diameter is, for example, about 40 mm to 65 mm. In this way, the electrode group 20 is formed.

4). As shown in FIG. 8, the positive electrode lead piece 21 c and the positive electrode current collector ring 40 are electrically connected. The positive electrode current collecting ring 40 is made of a disk-shaped conductive material (for example, aluminum or aluminum alloy). The positive electrode current collecting ring 40 has a central portion 40a and an outer ring portion 40b. A shallow concave portion 41 into which the shaft core 25 is fitted is provided in the central portion 40a on the first surface side (the upper surface in FIG. 8) of the positive electrode current collecting ring 40, and the second surface side opposite to the first surface side ( A concave portion 42 is provided in the central portion 40a of the lower surface in FIG. A convex portion (inside projection) 12 of the battery can 10 described later is fitted into the concave portion 42. The positive electrode lead piece 21 c is welded to the outer ring portion 40 b on the first surface side (the upper surface in FIG. 8) of the positive electrode current collecting ring 40. The outer ring portion 40b on the second surface side (the lower surface in FIG. 8) is also provided with a recess.

  Moreover, as shown in FIG. 8, the negative electrode lead piece 22c and the negative electrode current collection member 50 are electrically connected. The negative electrode current collecting member 50 is made of a conductive material (for example, copper or a copper alloy). The negative electrode current collecting member 50 includes a pole column part 51 and a flange part (also referred to as a ring part) 52. The pole column part 51 has an outer protrusion part 51a and an inner protrusion part 51b which are negative electrode external terminals. The outer protrusion 51a serves as a negative external terminal. The inner protrusion 51 b is fitted into the shaft core 25. The negative electrode lead piece 22c is welded to the bottom surface of the flange portion 52 (the surface on the inner protrusion 51b side). A concave portion is also provided on the upper surface of the flange portion 52 (the surface on the outer protrusion 51a side).

  Thereafter, an insulating coating (not shown) is formed by winding the side portions of the integrated positive electrode current collector ring 40, electrode group 20, and negative electrode current collector member 50 shown in FIG. To do. As the adhesive tape, for example, an adhesive tape in which the base material is polyimide and an adhesive material made of hexamethacrylate is applied on one surface thereof is used. The thickness of the insulating coating (number of turns of the adhesive tape) is adjusted so that the maximum diameter portion of the electrode group 20 covered with the adhesive tape is slightly smaller than the inner diameter of the battery can.

5. Insertion of Electrode Group into Battery Can The positive electrode current collecting ring 40, the electrode group 20, and the negative electrode current collecting member 50 which are covered with an insulating coating and integrated are inserted into the battery can. The battery can has an outer diameter of 67 mm and an inner diameter of 66 mm. Therefore, in this case, the thickness Tb of the battery can on the side surface is about 0.5 to 1 mm.

  The battery can 10 shown in FIG. 10 has a bottom surface, a side surface, and an opening. On the bottom surface of the battery can 10, the outer central portion has a convex portion 10 a serving as a positive electrode external terminal. A concave portion 11 is provided in the convex portion 10a. The recess 11 serves as a connection portion with a bolt (see FIG. 14), and a screw groove (not shown) is formed on the side surface thereof.

Further, on the bottom surface of the battery can, a convex portion (also referred to as an inner protrusion) 12 is provided at the inner central portion. The convex portion 12 is fitted into the concave portion 42 of the positive electrode current collecting ring 40. A safety valve 13 is provided on the outer periphery of the bottom surface of the battery can 10. The safety valve 13 is a recess provided on the outer peripheral portion of the bottom surface of the battery can 10, and the thickness of the battery can is smaller than the thickness of the battery can on the side surface (see FIG. 6C as well). reference). The safety valve 13 is cleaved as the internal pressure of the battery increases. The cleavage pressure is, for example, 13 to 18 kgf / cm ² .

  Such a battery can 10 is also formed by the impact molding method as in the case of the first embodiment. However, it is preferable that the recess 11, the screw groove on the side surface thereof, the recess constituting the safety valve 13, etc. are formed by cutting after the battery can 10 is formed by the impact molding method.

  Next, as shown in FIG. 11, the electrode group 20 is inserted from the opening of the battery can 10 with the positive electrode current collector ring 40 side as the lower side, and the convex part 12 on the bottom surface of the battery can is connected to the positive electrode current collector ring. It fits into the recess 42 of 40. Next, the contact portion between the convex portion 12 on the bottom surface of the battery can and the positive electrode current collecting ring 40 is connected by laser welding or the like.

6). Attaching the battery lid Next, the battery lid is attached to the opening of the battery can (FIG. 12). The ceramic washer 31, the battery lid 30 and the washer 32 are sequentially fitted into the outer protrusion (negative electrode external terminal) 51a of the negative electrode current collecting member 50 protruding from the opening of the battery can. The ceramic washer 31 is made of alumina, and the thickness of the portion in contact with the back surface of the battery lid 30 is 2 mm, the inner diameter is 16 mm, and the outer diameter is 25 mm. The washer 32 is made of, for example, ceramics or resin.

  Next, the peripheral end surface of the battery lid 30 is fitted into the opening of the battery can 10 and the entire area of both contact portions is welded and joined. At this time, the outer protrusion (negative electrode external terminal) 51 a of the negative electrode current collecting member 50 passes through a hole (hole) in the center of the battery lid 30 and protrudes to the outside of the battery lid 30.

  Next, the washer 32 is fitted into the outer protrusion (negative electrode external terminal) 51 a of the negative electrode current collecting member 50. The washer 32 is made of a material smoother than the bottom surface of the nut 33. Next, the metal nut 33 is screwed (screwed) into the outer protrusion (negative electrode external terminal) 51a.

7). Injection and Sealing of Electrolytic Solution Thereafter, the electrolytic solution is injected into the battery can 10 from a liquid injection port 30a (see FIG. 6B) provided in the battery lid 30, and the liquid injection port is sealed. As the electrolytic solution, for example, lithium hexafluorophosphate (LiPF ₆ ) is added in an amount of 1.2 mol / liter into a mixed solution in which ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate are mixed at a volume ratio of 2: 3: 2. Those dissolved in L can be used.

  Through the above steps, a cylindrical lithium ion battery can be formed.

  Thus, also in this Embodiment, the weight reduction of the battery can 10 can be achieved by using aluminum as a material of the battery can 10. In particular, aluminum has high spreadability, and the battery can 10 can be made thin. Also in this respect, the battery can 10 can be reduced in weight.

  Further, while the side surface of the battery can 10 is thinned (for example, a thickness of about 0.1 to 3.0 mm), the aluminum film is thickened (for example, a thickness of 10) at the convex portion 10a serving as the positive electrode external terminal. The external connection resistance can be reduced. In other words, the external connection resistance can be reduced by increasing the thickness of the positive external terminal in the height direction (for example, about 10 to 50 mm in thickness).

  Further, by connecting the battery can 10 side to the positive electrode, that is, the positive side of the electrode group 20, the electrode group 20 using the aluminum material as the positive electrode plate and the material of the battery can 10 become the same material, and their electrical stability. And electrical connectivity is improved. For example, the corrosion of the battery can can be suppressed as compared with the case where the positive electrode plate and the battery can are made of different materials. In particular, in a large-capacity lithium ion secondary battery, the charge / discharge reaction at the positive electrode is actively performed, so that the effect of improving the electrical stability at the positive electrode is great.

  Furthermore, the battery can 10 can be quickly formed in a short process by forming the battery can 10 by impact molding. FIG. 13 is a cross-sectional view showing a manufacturing process of a battery can by an impact molding method. Also in the case of forming the battery can of the present embodiment, the battery can is formed by driving the punch rod 103 into the aluminum material 101 as in the first embodiment (FIG. 3). However, here, a punch rod 103 having a hollow portion (also referred to as a recess) 103a at the center of the bottom portion is used. The depth of the hollow portion 103a is made larger than the height of the convex portion 12.

  Specifically, as shown in FIG. 13, first, the aluminum material 101 is set in the cavity 100 (the left diagram in FIG. 13). Next, a punch rod 103 having a diameter corresponding to the inner diameter of the battery can 10 and having a hollow portion 103a at the bottom is driven into the aluminum material 101 (center view in FIG. 13). Due to the impact of the punch rod 103 being driven, the aluminum material 101 flows and deforms and rises along the side surface of the punch rod 103 from the gap between the punch rod 103 and the cavity 100 (right diagram in FIG. 13). Further, the aluminum material 101 enters the hollow portion 103 a of the punch bar 103. The aluminum material 101 rising along the side surface of the punch bar 103 becomes a cylindrical side surface. Further, the aluminum material 101 that has entered the hollow portion 103 a of the punch rod 103 becomes the convex portion 12. Furthermore, the aluminum material 101 of the concave portion 100a becomes the convex portion 10a serving as the positive electrode external terminal at the central portion of the cavity. Thereafter, the battery can 10 can be formed by peeling the aluminum material 101 from the punch rod 103 and the cavity 100.

  Thus, also in this Embodiment, the battery can 10 can be rapidly formed by a short process by forming the battery can 10 by an impact molding method. Moreover, the battery can 10 can be rapidly formed by a short process by forming the convex part 12 and the convex part 10a used as a positive electrode external terminal collectively by an impact molding method.

(Embodiment 3)
In the first and second embodiments, one battery has been described. However, a plurality of batteries may be connected in parallel by using the nut 33 and the bolt 60 fitted into the recess 11.

  FIG. 14 is a cross-sectional view showing the configuration of the lithium ion secondary battery of the present embodiment. As shown in FIG. 14, a plurality of batteries are connected in parallel.

  For example, a plurality of batteries are connected using a plate (also referred to as a connecting member or a bus bar) 70 made of a rectangular conductive material (for example, copper or copper alloy) having a plurality of openings. Each battery is fixed by inserting an outer protrusion (also referred to as negative electrode external terminal) 51a of each battery through a washer 32 and screwing a nut 33 into the outer protrusion 51a. On the other hand, on the positive electrode side, a plate-like member 61 made of a rectangular conductive material (for example, aluminum or aluminum alloy) having a plurality of openings is used, and the openings and the recesses 11 of the batteries are aligned. The recess 11 is provided with a screw groove (not shown). The bolts 60 are screwed into the recesses 11 to be fixed.

  As described above, even when a plurality of batteries are connected, the external connection resistance can be reduced by increasing the thickness of the aluminum film of the convex portion 10a serving as the positive electrode external terminal. In particular, when a plurality of batteries are connected, the influence of the external connection resistance of each battery is large. For example, in a large-scale power storage system using 20 or more batteries, the configuration of this embodiment is effective. Is.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiments and examples. However, the present invention is not limited to the above-described embodiments and examples, and does not depart from the gist of the invention. Various changes can be made.

  The present invention is effective when applied to a lithium ion secondary battery.

DESCRIPTION OF SYMBOLS 10 Battery can 10a Convex part 11 Concave part 12 Convex part 13 Safety valve 20 Electrode group 21 Positive electrode plate 21a Current collector 21b Positive electrode mixture 21c Positive electrode lead piece 22 Negative electrode plate 22a Current collector 22b Negative electrode mixture 22c Negative electrode lead piece 23, 24 Separator 25 Axle 30 Battery cover 30a Injection port 31 Ceramic washer 32 Washer 33 Nut 40 Positive electrode current collecting ring 40a Center part 40b Outer ring part 41 Recess 42 Recess 50 Negative electrode current collecting member 51 Polar column part 51a Outer protrusion part 51b Inner protrusion part 52 Gutter 60 Bolt 61 Plate-like member 70 Plate 100 Cavity 100a Recess 101 Aluminum material 103 Punch rod 103a Hollow part

Claims (11)

A cylindrical battery container that houses an electrode group, the battery container having a bottom, a side, and an opening;
A battery lid that seals the opening of the battery container;
The battery container is made of a material containing aluminum,
A positive external terminal is provided at the bottom of the battery case,
On the battery lid side, a negative external terminal is provided,
A thickness of the positive electrode external terminal in the height direction is a secondary battery that is thicker than a thickness of a side portion of the battery container. The secondary battery according to claim 1,
The secondary battery is a secondary battery, which is a lithium ion secondary battery. The secondary battery according to claim 2,
The electrode group includes a positive electrode plate,
The positive electrode plate has a current collector made of a material containing aluminum,
A positive electrode lead piece is provided at an end of the current collector,
The secondary battery, wherein the positive electrode lead piece is electrically connected to the positive external terminal at the bottom of the battery container. The secondary battery according to claim 3,
The positive electrode external terminal is provided with a recess,
A secondary battery having a bolt connected to the recess. (A) a step of forming an electrode group by winding the positive electrode plate and the negative electrode plate through a separator;
(B) A cylindrical battery container, and the electrode group is housed in the battery container such that the positive electrode side of the electrode group contacts the bottom part in a battery container having a bottom part, a side part, and an opening part. Process,
(C) sealing the opening of the battery container with a battery lid,
The battery container is made of a material containing aluminum,
A positive external terminal is provided at the bottom of the battery case,
The thickness of the said positive electrode external terminal is a manufacturing method of a secondary battery thicker than the thickness of the side part of the said battery container. In the manufacturing method of the secondary battery according to claim 5,
The secondary battery is a method of manufacturing a secondary battery, which is a lithium ion secondary battery. In the manufacturing method of the rechargeable battery according to claim 6,
The battery container is a method for manufacturing a secondary battery, which is formed by an impact molding method. In the manufacturing method of the secondary battery according to claim 7,
The battery container causes the aluminum-containing material to flow deform by an impact when the rod-shaped member is driven into the aluminum-containing material, and raises the aluminum-containing material along the side surface of the rod-shaped member. The manufacturing method of the secondary battery formed by this. In the manufacturing method of the secondary battery according to claim 8,
The positive electrode plate has a current collector made of a material containing aluminum,
A positive electrode lead piece is provided at an end of the current collector,
In the step (b), the positive electrode lead piece is electrically connected to the positive external terminal at the bottom of the battery container. In the manufacturing method of the secondary battery according to claim 8,
The rod-shaped member is driven into a cavity in which the material containing aluminum is disposed,
The cavity has a recess;
The method for manufacturing a secondary battery, wherein the positive electrode external terminal is formed corresponding to the recess. In the manufacturing method of the secondary battery according to claim 8,
The rod-shaped member has a hollow portion,
A method for manufacturing a secondary battery, wherein a convex portion corresponding to the hollow portion is formed on the positive electrode external terminal.

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